| 摘要 |
1,248,954. A/D converters. BAXTER LABORATORIES Inc. 4 Oct., 1968 [13 Oct., 1967], No. 47080/68. Heading G4H. An analogue/digital converter includes a counter/printer 18 (Fig. 2) receiving a train of pulses until a reference ramp signal from ramp generator 108 equals the analogue input signal. In one embodiment on depression of a start switch 50, the ramp generator 108 feeds a linearly varying signal to comparator 106 for comparison with the output of a spectrophotometer 104, a contact A being simultaneously closed to feed cycles of the mains signal via a diode 103 to the solenoid 20 of units print wheel in printer 18, carry pulses being transmitted to the tens and hundreds solenoids 24, 28. On equality relay K2 is operated to earth the units solenoid and energize a print solenoid 30 so that the count is printed on paper tape. In the embodiment of Fig. 3, the ramp signal is derived from a capacitor so that the printed output is logarithmically related to the input. Calibration is effected by testing a blank sample such as pure water and adjusting manually the gain of operational amplifier 200 via the potentiometer 202. A standard sample is then tested and resistor R is adjusted until the printer prints the correct reading. |
